The invention relates generally to a method and apparatus for securing a tubular sleeve coaxially within a fluid conduit.
There exists, in a variety of embodiments, fluid conduits which themselves are surrounded by a fluid environment. One such example is that of a tube and shell heat exchanger wherein a first fluid is contained within the fluid conduit and a second fluid surrounds the exterior of the conduit such that heat exchange between the two fluids is effected. Such fluid conduits may from time to time develop leaks due to rupturing of the conduit wall, which may occur due to initial imperfections or through subsequent deterioration of the conduit. The resulting leak permits fluid communication between the first and second conduits which may not always be tolerable. Such would be the case if the two fluids in combination reacted violently or if one fluid would introduce some undesirable property to the second fluid. An example of this latter problem arises in the steam generating heat exchangers associated with pressurized water nuclear steam supply wherein the fluids are at substantially different pressures and one fluid contains radioactivity while the other does not. For these reasons, continued, large amounts of fluid communication between the two fluids through a leak in the tube must be prevented.
When the fluid conduits are readily accessible, a variety of techniques may be employed to repair the ruptured conduit directly or to install a sleeve device or a plug into the conduit which stops the leak or completely isolates the entire conduit from a fluid source. However, in some environments, including that of a nuclear heat exchanger, it may be difficult for reasons of inaccessibility or biological hazard to effect such repairs. In such instances, techniques have been developed for plugging the fluid conduits from a remote location and thus totally removing them from service. Either rolling, explosive expansion and/or welding have been used to secure plugs in the tube ends. Rolling and welding are rather difficult to apply as remote operation and explosive expansion has emerged as the most viable means of plugging tubes by remote operation.
A serious drawback to plugging both ends of a heat exchanger tube is that eventually as more and more tubes are plugged the capacity of the steam generator becomes less and less. Plugging requires removing an entire tube from operation when in general only a small localized zone of the tube is involved in the leak. Attempts have been made to install sleeving within the tube to isolate the portion of the tube which has degraded thereby stopping the leak. Previous sleeving development work has been primarily concerned with obtaining an absolutely leak proof joint by brazing, arc welding, explosive welding, or some other means. All of these metallurgical bonding techniques have problems which are not immediately amendable except in very closely controlled laboratory situations. This is due to the need for cleanliness, close fittings, heat application and atmosphere control.